1. Field of the Invention
The present invention relates to an integrated circuit device in which a battery made of solid-state electrolyte is mounted on a semiconductor chip to supply power to the integrated circuit during usual time or power failure.
2. Discussion of the Related Art
With development of small-size, light-weight, and portable electronic devices, demands for battery power-supplies have been advanced to improve case of their use. Both primary and secondary batteries are used as the battery for a power supply. In both cases, the battery is required to be small-sized, light-weight and have long usable time. Usually, the battery uses a liquid electrolyte or an electrolytic layer impregnated with an electrolyte. However, since it must be sealed in a package, its bulk and weight increase. Such a battery is not suitable for portable electronic devices. For this reason, in recent years, attention has been paid to the future of the battery using solid electrolyte.
Previously known electrolytes suitable to such a battery include e.g. natrium-ion conductive ones of a gallia or alumina series (Japanese Patent Unexamined Publication No. Sho 57-27982), lithium-ion conductive ones of a lithium compound series (Japanese Patent Unexamined Publication Nos. Sho 59-31569, 59-31570 and 59-60866), copper-ion conductive ones such as a copper halide series and silver-ion conductive ones such as a silver compound series (Japanese Patent Unexamined Publication No. Sho 63-34864), and also includes several materials, particularly metal ion conductive ones. By stacking these solid electrolytic thin films several .mu.ms or so thick together with a negative pole (cathode) metallic film and a metallic film for connection, a very thin battery in a thin film laminated structure of 10 .mu.m thick or less, although now not having a large current capacity, can be made. Incidentally, since the conductivity of the solid electrolyte is a function of temperature, the current capacity of the battery can be improved by raising its operating temperature.
The above solid electrolytic battery is suitable for small power supplies. However, since the electronic devices in which such a battery is to be incorporated, particularly, portable ones are required to be downsized, the space in which the battery is to be provided must be minimized. Further, in many cases, in order to advance the function of the electronic device, a display and/or a printer is incorporated into the device, and driving capability for external loads may be added. For this reason, frequently, it is necessary to supply plural voltages to circuits within the electronic device. In order to supply these plural voltages, a DC-DC converter such as a known switching power source must be incorporated. However, its voltage conversion operation necessarily brings about power loss so that the life of the primary battery or the dischargeable time of the secondary battery will be shortened. A precious space must be also used to incorporate the converter.
On the basis of the fact that the solid electrolytic battery is suitable for supply small power, using it for back-up, i.e., as a power source during power failure of the normal power source for an electronic device, or during its movement time, makes it possible for the electronic device to hold the storage content of its RAM or to always maintain its sensing function. In this case, there is no problem involved with the converter for voltage conversion. However, if the secondary battery is used for back-up so that a necessary space inclusive of the circuit for its charge/discharge or power supply switching must be minimized.